Digital cinema projection systems are often used to display motion pictures in commercial movie theaters. Typically, such systems comprise a digital video projector and a playback server that provides digital content to the projector. In typical projection systems, this content is supplied from the server to the projector over one or more video links, such as a high-definition serial digital interface (“HD-SDI”) or digital video interface (“DVI”) connection. To prevent, or at least minimize, unauthorized access of the content, the digital content is often encrypted for transport over the one or more video links using an Advanced Encryption System (“AES”) based local link encryption system.
In particular projection systems, proper operation of the AES-based local link encryption system requires a mechanism to transport ancillary data, such as time-critical control data, from the server to the projector. Many video links, such as HD-SDI, provide a dedicated ancillary data subchannel. However, other video links, such as DVI, do not. In these other video links, other mechanisms for transporting the ancillary data must be used.